A flexible conductive hydrogel and a preparation method and application thereof

Abstract

The present application relates to a kind of flexible conductive hydrogel and its preparation method and application, PEDOT:PSS phase separation is induced using polyacid, and is prepared by annealing complex solvent method.The hydrogel provided in the present application exhibits excellent electromagnetic shielding efficiency in X, Ku and K band, and the mechanical tensile performance is excellent, has wide application prospect in wearable, flexible electronic communication and other fields.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave shielding materials, and specifically relates to a flexible conductive hydrogel, its preparation method, and its application. Background Technology

[0002] The rapid development of electronic communication technology has brought convenience to people, but it has also brought serious electromagnetic radiation, which not only affects the normal operation of electronic devices but also harms human health. Developing high-performance electromagnetic interference (EMI) resistant materials has become one of the most effective ways to alleviate the increasingly serious problem of electromagnetic pollution. Electromagnetic shielding materials, with their high conductivity and strong loss characteristics, can effectively reflect and absorb incident electromagnetic waves, thereby attenuating them and reducing their penetration ability. This characteristic not only effectively protects electronic components exposed to electromagnetic radiation from interference and attacks, but also enhances the EMI and electronic attack resistance of electronic devices, strengthens their electromagnetic compatibility, and is of great significance to communication system security, human health, and environmental protection. In recent years, with the rapid development of portable devices and wearable electronic products, traditional rigid electromagnetic shielding materials can no longer meet application requirements. To address the bendability, stretchability, and compressibility of flexible devices, there is an urgent need to develop flexible electromagnetic protection materials with high shielding effectiveness.

[0003] Hydrogels are three-dimensional network structures formed by the physical or chemical cross-linking of polymer chains. Their excellent flexibility and processability have attracted widespread attention in fields such as medicine, environmental science, and flexible electronics. Among them, conductive hydrogels with high electron transport characteristics can effectively enhance conductivity loss and cause electromagnetic waves to be reflected on the material surface, thereby effectively reducing the impact of electromagnetic radiation on the environment and human body. They are electromagnetic shielding materials with great application prospects for flexible electronic devices. Conductive hydrogels are generally divided into filled and intrinsically conductive types. The preparation method of filled conductive hydrogels is to add inorganic conductive fillers to an insulating polymer substrate to improve the conductivity of the hydrogel. Common conductive fillers include graphene oxide, carbon nanotubes, MXene nanosheets, and silver nanowires. For example, Yu et al. prepared an organic hydrogel containing MXene nanosheets with a conductivity of 0.442 S / m and an electromagnetic shielding effectiveness of up to 37 dB (Yu Y, et al. Nano-Micro Letters, 2022, 14(1):77.). Although inorganic conductive fillers can effectively improve conductivity, their dispersibility deteriorates during long-term polymerization, leading to aggregation or recombination and a decrease in the mechanical properties of organic hydrogels. Intrinsic conductive hydrogels, on the other hand, are prepared directly using conductive polymers as the matrix. Wang et al. prepared conductive hydrogels doped with ionic liquids using PEDOT:PSS as the matrix and a dry annealing and rehydration method. The conductivity reached 305 S / cm, and the electromagnetic shielding effectiveness was 54 dB. Anions in the ionic liquid can partially replace PSS, causing nanophase separation of PEDOT:PSS, thereby improving conductivity (Wang J, et al. Advanced Materials, 2022, 34(12): 2109904.). However, the maximum strain of this hydrogel is only about 30%, which is insufficient to meet the mechanical performance requirements of flexible devices. Therefore, it is urgent to develop electromagnetic shielding hydrogels with both high conductivity and good tensile strength to meet the application needs of flexible electronic devices and wearable devices in the field of electromagnetic interference resistance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a flexible conductive hydrogel, its preparation method and application, which solves the problem that it is difficult to uniformly combine inorganic conductive fillers with flexible polymer matrix in current filled conductive hydrogels, as well as the problem that the mechanical properties of intrinsically conductive polymer-based hydrogels are not good.

[0005] This invention provides a flexible conductive hydrogel, which is prepared by using polyacid-induced phase separation of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid PEDOT:PSS and annealing resolvent method.

[0006] Preferably, the polyacid is phosphotungstic acid.

[0007] This invention also provides a method for preparing a flexible conductive hydrogel, comprising the following steps:

[0008] (1) Dissolve the polyacid in a solvent by ultrasonic dispersion to obtain a polyacid solution; then add the resin to the polyacid solution, heat in an oil bath and reflux to make the resin fully dispersed in the polyacid solution, and finally cool the mixed solution to room temperature for later use.

[0009] (2) The mixed solution obtained in step (1) is mixed with PEDOT:PSS to form a pregel, annealed at 90-95℃ for 2-6h, and then a solvent is added to obtain a flexible conductive hydrogel.

[0010] Preferably, the concentration of the polyacid solution in step (1) is 0.1-0.3 mol / L.

[0011] Preferably, the resin in step (1) is polyvinyl alcohol; the mass fraction of the resin in the mixed solution is 6%-12%.

[0012] Preferably, the ultrasound time in step (1) is 10-20 min.

[0013] Preferably, the oil bath heating temperature in step (1) is 95°C and the time is 2 hours.

[0014] Preferably, the volume ratio of the mixed solution and the conductive polymer in step (2) is 1:3.

[0015] Preferably, the solvent in step (1) is a mixture of water and glycerol in a volume ratio of 1:0.1-1.

[0016] Preferably, the solvent in step (2) is a mixture of water and glycerol in a volume ratio of 1:0-1.

[0017] The present invention also provides an application of flexible conductive hydrogel in the fields of microwave anechoic chambers, military stealth and electromagnetic protection.

[0018] Beneficial effects

[0019] (1) This invention utilizes polyacid-induced phase separation of PEDOT:PSS and prepares a conductive hydrogel capable of efficiently shielding multi-band electromagnetic waves via an annealing-resolvent method. The polyacid can partially remove non-conductive PSS from the conductive polymer PEDOT:PSS, effectively increasing the conductivity of the hydrogel. Compared with traditional hydrogel preparation processes, this method has a shorter preparation cycle and a simpler process flow.

[0020] (2) The hydrogel prepared by this invention has a unique microstructure. The polyacids induce the formation of a continuous conductive network of PEDOT:PSS, thereby enhancing the conductivity loss and allowing the incident electromagnetic waves to dissipate rapidly as heat. In addition, the abundant polar water molecules, glycerol, and polyacids in the hydrogel provide abundant polarization centers, which is conducive to dipole polarization and significantly improves the electromagnetic shielding performance of the composite material. The hydrogel prepared by this invention has excellent electromagnetic shielding effectiveness, with total specific electromagnetic shielding effectiveness (SSET) reaching 104.74 dB / mm, 104.74 dB / mm, and 127.52 dB / mm in the X, Ku, and K bands, respectively. Moreover, the shielding performance is mainly absorption-based, effectively reducing secondary electromagnetic pollution.

[0021] (3) The present invention uses polyvinyl alcohol as an additive, which effectively improves the mechanical properties and environmental stability of the hydrogel and develops a flexible electromagnetic shielding hydrogel for practical applications. Attached Figure Description

[0022] Figure 1 The image shows a SEM image of the PWP0 flexible conductive hydrogel prepared in Example 1.

[0023] Figure 2 The PWP0 flexible conductive hydrogel prepared in Example 1 was used in X-ray band SSE. T SSE A and SSE R Test results.

[0024] Figure 3 The PWP0 flexible conductive hydrogel prepared in Example 1 was used in the Ku-band SSE. T SSE A and SSE R Test results.

[0025] Figure 4 The stress-strain curve of the PWP0 flexible conductive hydrogel prepared in Example 1 is shown.

[0026] Figure 5 The PWP20 flexible conductive hydrogel prepared in Example 2 was used in X-ray band SSE. T SSE A and SSE R Test results.

[0027] Figure 6 The PWP20 flexible conductive hydrogel prepared in Example 2 was used in the Ku-band SSE. T SSE A and SSE R Test results.

[0028] Figure 7The stress-strain curve of the PWP20 flexible conductive hydrogel prepared in Example 2 is shown.

[0029] Figure 8 The PWP60 flexible conductive hydrogel prepared in Example 3 was used in X-ray band SSE. T SSE A and SSE R Test results.

[0030] Figure 9 The PWP60 flexible conductive hydrogel prepared in Example 3 was used in the Ku-band SSE. T SSE A and SSE R Test results.

[0031] Figure 10 The PWP60 flexible conductive hydrogel prepared in Example 3 was tested in the K-band SSE. T SSE A and SSE R Test results.

[0032] Figure 11 The stress-strain curve of the PWP60 flexible conductive hydrogel prepared in Example 3 is shown.

[0033] Figure 12 The PWP100 flexible conductive hydrogel prepared in Example 4 was used in X-ray band SSE. T SSE A and SSE R Test results.

[0034] Figure 13 The PWP100 flexible conductive hydrogel prepared in Example 4 was used in Ku-band SSE. T SSE A and SSE R Test results.

[0035] Figure 14 The stress-strain curve of the PWP100 flexible conductive hydrogel prepared in Example 4 is shown. Detailed Implementation

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] Example 1

[0038] (1) Weigh 4.725g (0.15mol / L) phosphotungstic acid (hereinafter referred to as PW). 12 1g of polyvinyl alcohol (PVA) and 1g of glycerol were dissolved in a mixed aqueous solution of 5ml H2O and 5ml glycerol, and stirred thoroughly at 95℃ for 2 hours to form PW. 12 / PVA aqueous solution.

[0039] (2) Subsequently, it was mixed with PEDOT:PSS aqueous dispersion at a volume ratio of 1:3 and stirred thoroughly at room temperature for 2 min to form a pregel. After sealing, it was annealed at 90°C for 2.5 h, and then immersed in water to obtain a flexible conductive hydrogel. Test results: The morphology of the hydrogel prepared in this embodiment was characterized by scanning electron microscopy (SU8010, Hitachi, Japan). Figure 1 As shown, polyacids induce the formation of a unique three-dimensional network structure inside the PEDOT:PSS hydrogel.

[0040] The hydrogel prepared in this embodiment was cut into cuboid samples with dimensions of 22.9 mm × 10.2 mm and 15.9 mm × 8.03 mm (length × width), with unlimited thickness, using a mold. The shielding performance of the samples in the 8.2-12.4 GHz and 12.4-18 GHz ranges was tested using a vector network analyzer (Keysight, N5234B). Figure 2 , 3 As shown, the concentration of PVA / PW is 0.15 mol / L. 12 PEDOT-GLY 0% hydrogel (PWP0 for short) has a total specific electromagnetic shielding effectiveness (SSE) in the 8.2-12.4 GHz band. T = 58.42dB / mm, where SSE A = 48.27dB / mm, SSE R =10.15dB / mm; Overall specific electromagnetic shielding effectiveness (SSE) in the 12.4-18GHz band. T = 55.55dB / mm, where SSE A = 46.43dB / mm, SSE R = 9.12dB / mm.

[0041] The conductivity of the hydrogel prepared in this embodiment was measured to be 14.07 S / cm using the four-probe method.

[0042] The hydrogel prepared in this embodiment was tested using an electronic universal testing machine (INSTRON / 5969) to obtain the stress-strain curve of the sample, as shown below. Figure 4 As shown, PWP0 has a maximum elongation at break of 33.2% and a Young's modulus of 0.12 MPa.

[0043] Example 2

[0044] The difference between this embodiment and Embodiment 1 is that after annealing, it is soaked in a 20% glycerol aqueous solution; otherwise, they are the same as in Embodiment 1.

[0045] Test Results: The hydrogel prepared in this embodiment was cut into cuboid samples with dimensions of 22.9mm × 10.2mm and 15.9mm × 8.03mm (length × width), respectively, with unlimited thickness. The shielding performance of the samples in the 8.2-12.4GHz and 12.4-18GHz ranges was tested using a vector network analyzer (Keysight, N5234B). Figure 5 , 6 As shown, the concentration of PVA / PW is 0.15 mol / L. 12 PEDOT-GLY 20% (PWP20) hydrogel exhibits superior overall specific electromagnetic shielding (SSE) performance in the 8.2-12.4 GHz band. T = 80.88dB / mm, where SSE A =68.59dB / mm, SSE R =12.29dB / mm; Overall specific electromagnetic shielding effectiveness (SSE) in the 12.4-18GHz band. T = 72.08 dB / mm, where SSE A =61.72dB / mm, SSE R =10.36dB / mm.

[0046] The conductivity of the hydrogel prepared in this embodiment was measured to be 3.75 S / cm using the four-probe method.

[0047] The hydrogel prepared in this embodiment was tested using an electronic universal testing machine (INSTRON / 5969) to obtain the stress-strain curve of the sample.

[0048] like Figure 7 As shown, PWP20 has a maximum elongation at break of 68.3% and a Young's modulus of 0.12 MPa.

[0049] Example 3

[0050] The difference between this embodiment and Embodiment 1 is that after annealing, it is soaked in a 60% glycerol aqueous solution; otherwise, they are the same as in Embodiment 1.

[0051] Test Results: The hydrogel prepared in this embodiment was cut into cuboid samples with dimensions of 22.9mm × 10.2mm, 15.9mm × 8.03mm, and 10.95mm × 4.5mm (length × width), and unlimited thickness, respectively, using a mold. The shielding performance of the samples in the ranges of 8.2-12.4GHz, 12.4-18GHz, and 18-26.5GHz was tested using a vector network analyzer (Keysight, N5234B). Figure 8 , 9 As shown in Figure 10, the concentration of PVA / PW is 0.15 mol / L. 12 The overall specific electromagnetic shielding effectiveness (SSET) of PEDOT-GLY 60% (PWP60) hydrogel in the 8.2-12.4 GHz band is 105.31 dB / mm, where SSE... A = 86.01dB / mm, SSE R =19.30 dB / mm; Overall specific electromagnetic shielding effectiveness (SSE) in the 12.4-18 GHz band. T =104.10dB / mm, where SSE A = 86.48dB / mm, SSE R =17.62dB / mm; Overall specific electromagnetic shielding effectiveness (SSE) in the 18-26.5GHz band. T =129.52dB / mm, where SSE A =116.17dB / mm, SSE R =13.35dB / mm.

[0052] The conductivity of the hydrogel prepared in this embodiment was measured to be 15.65 S / cm using the four-probe method.

[0053] The hydrogel prepared in this embodiment was tested using an electronic universal testing machine (INSTRON / 5969) to obtain the stress-strain curve of the sample, as shown below. Figure 11 As shown, PWP60 has a maximum elongation at break of 96.9% and a Young's modulus of 0.43 MPa.

[0054] Example 4

[0055] The difference between this embodiment and Embodiment 1 is that after annealing, it is soaked in a 100% glycerol aqueous solution; otherwise, they are the same as in Embodiment 1.

[0056] Test Results: The hydrogel prepared in this embodiment was cut into cuboid samples with dimensions of 22.9mm × 10.2mm and 15.9mm × 8.03mm (length × width), respectively, with unlimited thickness. The shielding performance of the samples in the 8.2-12.4GHz and 12.4-18GHz ranges was tested using a vector network analyzer (Keysight, N5234B). Figure 12 , 13 As shown, the concentration of PVA / PW is 0.15 mol / L. 12 PEDOT-GLY 100% (PWP100) hydrogel exhibits superior overall specific electromagnetic shielding (SSE) performance in the 8.2-12.4 GHz band. T = 93.15 dB / mm, where SSE A =74.93dB / mm, SSE R =18.22dB / mm; Overall specific electromagnetic shielding effectiveness (SSE) in the 12.4-18GHz band. T = 93.15 dB / mm, where SSE A = 81.03dB / mm, SSE R =12.12dB / mm.

[0057] The conductivity of the hydrogel prepared in this embodiment was measured to be 2.61 S / cm using the four-probe method.

[0058] The hydrogel prepared in this embodiment was tested using an electronic universal testing machine (INSTRON / 5969) to obtain the stress-strain curve of the sample, as shown below. Figure 14 As shown, PWP100 has a maximum elongation at break of 64.6% and a Young's modulus of 0.99 MPa.

[0059] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A flexible conductive hydrogel, characterized in that: The polyacid is phosphotungstic acid.

2. A method for preparing the flexible conductive hydrogel according to claim 1, comprising the following steps: (1) ultrasonic dispersion of the polyacid in a solvent to obtain a polyacid solution; then adding a resin into the polyacid solution, heating in an oil bath and conducting a condensation reflux to make the resin fully dispersed in the polyacid solution, and finally cooling the mixed solution to room temperature for standby; (2) mixing the mixed solution obtained in step (1) with PEDOT:PSS to form a pre-gel, annealing at 90-95℃ for 2-6h, adding a solvent to obtain the flexible conductive hydrogel.

3. The method of claim 2, wherein: The concentration of the polyacid solution in step (1) is 0.1-0.3mol / L.

4. The method of claim 2, wherein: The resin in step (1) is polyvinyl alcohol; the mass fraction of the resin in the mixed solution is 6%-12%.

5. The method of claim 2, wherein: The ultrasonic time in step (1) is 10-20min.

6. The method of claim 2, wherein: The solvent in step (1) is a mixed solvent of water and glycerol in a volume ratio of 1:0.1-1.

7. The method of claim 2, wherein: The solvent in step (2) is a mixed solvent of water and glycerol in a volume ratio of 1:0-1.

8. The method of claim 2, wherein: The volume ratio of the mixed solution to PEDOT:PSS in step (2) is 1:

3.

9. Use of the flexible conductive hydrogel according to claim 1 in the field of microwave darkroom, military stealth and electromagnetic protection.

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